1. Field of the Invention
This invention relates to terpolymers of a vinyl lactam, a polymerizable carboxylic acid and a hydrophobic monomer, and, more particularly, to precipitation polymerization of such terpolymers within a defined compositional range, prepared in high yield, as a white powder, which can be filtered and dried easily.
2. Description of the Prior Art
Terpolymers of vinyl lactams, e.g. vinyl pyrrolidone or vinyl caprolactam, polymerizable carboxylic acids, e.g. acrylic acid or methacrylic acid, and hydrophobic monomers, e.g. alkyl vinyl ethers, have found application in the photographic industry, as coatings, as biological membranes, in drug release systems, as preservatives, in oil recovery processes, in immunochemicals, and in cosmetic materials.
For example, Straub, F. et al. in U.S. Pat. No. 4,595,737 prepared water soluble terpolymers of a vinyl lactam, acrylic acid and 50-80% of a C.sub.1 -C.sub.4 alkyl vinyl ether by solution polymerization in alcohol or a cyclic ether.
Blank, I. in U.S. Pat. No. 4,482,534, disclosed a solution polymerization process in cyclohexane for preparing terpolymers comprising 62.5% vinyl pyrrolidone, 5% acrylic acid and 32.5% lauryl methacrylate. The product was a viscous mass which was very difficult to filter; it was isolated by casting a film of the terpolymer and evaporating the solvent.
Blank, I. and Fertig, J., in U.S. Pat. No. 4,248,855, described a series of terpolymers of vinyl pyrrolidone, acrylic acid and methyl acrylate, prepared by solution and emulsion polymerization.
Other references of interest in this field include U.S. Pat. Nos. 3,044,873; 3,862,915; 4,283,384 and 4,737,410.
The terpolymer products made by these solution and emulsion polymerization methods, however, were not amenable to ready recovery of the polymer in high yield and in the form of a powder.
Precipitation polymerization is a known method for preparing polymers as a powder which can be filtered and dried easily; it is available when the monomers are adequately soluble in the reaction solvent and the polymer is insoluble in the solvent. A commercially successful precipitation polymerization process, however, must provide a precipitate of the polymer as a powder, in a non-toxic solvent, in high yield, which is easy to filter, and within a desired polymer compositional range.
Accordingly, it is an object of this invention to provide a precipitation polymerization process for making terpolymers comprising a vinyl lactam monomer, a polymerizable carboxylic acid monomer and a hydrophobic monomer, which precipitation polymerization process provides the terpolymer as a powder which is easy to filter, in high yield, in a non-toxic solvent, and within predetermined compositional ranges of monomer constituents.